Die-casting or injection molding machine



Dec. 23, 1952 W. A. VENUS DIE-CASTING OR INJECTION MOLDING MACHINE Filed Sept. 28, 1949 2 SHEETS-SHEET 1 INVENTORI W/L/BALDAVENUS ATTORNEYS 2 SHEETS-SHEET 2' W. A. VENUS DIE-CASTING OR INJECTION MOLDING MACHINE Dec. 23, 1952 Filed Sept. 28, 1949 myENToR W/L IBALDAJ ENUS Wm A gzz/ Patented Dec. 23, 1952 UNITED STATES PATENT OFFICE DIE-CASTING R INJECTION MOLDING MACHINE Wilibald A. Venus,Munich,"Germany, assignor to Hahn & Kolb, Stuttgart N, Germany Claims.

This invention relates to die-casting machines and injection moulding machines and more particularly to piston-operated, especially hydraulically operated, machines comprising one or a plurality of dies laterally arranged with regard to direction when the molten metal is admitted to the sprue.

Known are machines of this type, in which an operating piston controls the movement of the opposed plunger in such a way that the injection plunger actuates a valve shortly before coming intoco-ntact with the molten metal, whereby the opposed plunger is free to move. It is the object of this arrangement to have the sprue opened by the opposed plunger independent of the pressure in the material chamber. As it is impossible to reliably control the starting sequence of operations in view of their being dependent of inertia, friction heads in conduits, valvesand other parts and because of the impracticability of accurate adjustment with the equipment available in the shop, it has proved virtually impossible to set these machines in such a way that on the one hand the opposed plunger begins its motion of opening thesprue always at the very moment when the injection plunger approaches the molten metal-before however getting into actual contact therewithand that on the other'hand the opposed plunger travels with the same speed as the injection plunger following the receding molten metal. Thus it happens that the prior constructions with valvecontrolled opposed pistons often show thesame drawback as machines with spring-mounted opposed plungers: the injection plunger comes prematurely intocontact with the molten metal and produces a very high pressure before the opposed .pistonstarts moving. The fact that adjustment cannot be carried out correctly may, on the other hand, have the opposite effect, in that the opposedplunger starts moving before the injection plunger has arrived directly over the 'molten metal. 'When the opposed plunger carries out sucha leading motion, part of the molten metal flows into' the prematurely opened sprue, where itsolidifies and clogs the sprue, with the result that the, remainder of the-molten metal forced into-the sprue bythe pressure of theplunger is no longer allowed to pass to the die. Besides,

the air between injection plunger and molten metal is trapped and pressed into the dies, causing porous spots and blow holes.

All these drawbacks and difficulties are practically avoided according to the invention in that transmitting means which, just before the injection plunger touches the molten metal, are positively actuated by-said plunger for the purpose of moving the opposed plunger and opening the sprue, are so connected to the opposed plunger that the latter on the one hand opens the sprue through a bias existing between said plunger and the transmission means, and that on the other hand the transmitting means can follow the continued motion of the injection plunger when the motion of the'opposed plunger is arrested.

It is advantageous to arrange the connection between the opposed plunger and the transmittingmeans in such a manner that the opposed plunger is yieldingly pressed against a stop provided on the transmitting means, and that the transmitting means are yieldingly pressed with a higher pressure against a, stop arranged in the upward direction, the injection plunger being adapted to lift these transmitting means from the stop by positive'action.

'Ina preferred embodiment of the yielding action on the opposed plunger and the transmitting means, the arrangement is such that pistons of variouscross sections connected with these transmitting means are-subjected to pressure. from a common pressure chamber. It is advantageous to locate 'the common pressure chamber in a combined cylinder-piston which effects the outward and inward movement of the opposed plunger in the compression chamber.

In a preferred embodiment of the invention the forward stroke of the combined cylinderpiston is jointly controlled with that of the die closing pistonin such a way that, through proper dimensioning of the cross sections of the pistons, the combined. cylinder-piston carries out its outward motion before the die closing piston opens the die.

In thefollowing the invention is describedin accordance with an embodiment of the invention shown in the drawing, the description mamfesting vother characteristic objects of the invention.

Fig. 1 shows a vertical longitudinal section of a die-casting machine;

Fig. 2shows a verticallongitudinal section in a planeperpendiculantothat ofFig. 1 andwith other positions of-the pistons.

I .is 1 a cylindrical "material 7 and compression chamber mounted in the machine frame 25. The machine frame 25 is connected by tie rods 23 to a die closing cylinder 3% represented in Fig. 2, whose closing piston 35 closes or opens die 32, 33, which is laterally arranged with respect to the material and compression chamber. it is a sprue connecting chamber I with die half 32.

Into a hydraulic compression cylinder 2E3 arranged on top and subjected to pressure by the pressure fluid extends a piston I9 rigidly connected with the cross head It to which an injection plunger 2 is detachably mounted by means of flange 2i. Two push rods 3 with stop collars fastened to the cross head I4 extend with their lower ends into corresponding holes in bridge I2.

The opposed plunger 3 serving as bottom of the material and compression chamber I is connected to piston 9 through piston rod l. Nut i8 and lock nut Il are arranged on piston rod 4. 5 is a ring-shaped piston. A combined cylinderpiston I serves as cylinder for the two pistons 5 and 9. The common pressure chamber 25 of pistons 5 and 9 is permanently connected, through port 29, with the ring-shaped space Iii. A constant pressure liquid supply line supplies pressure to this space it and, at the same time, to ringshaped space 2 3, said pressure causing piston E9 to return to its starting position. 30 is a stop on frame 25 for limiting the upward travel of bridge I2 and ring-shaped piston 5 in combined cylinder-piston l. 8 is a stop in combined cylinder-piston I for piston 9. Below combined cylinder-piston l is a pressure chamber 27 exerting a pressure on the large lower face of combined cylinder-piston l and connected to the closing cylinder 35 of the die closing piston.

To pressure chamber 2? of cylinder II and to the pressure chamber of die closing cylinder 36 pressure is transmitted through a conventional control. mechanism at.

The operating principle of the machine is as follows:

When the die 32, 33 is closed by control mechanism 48, the die closing piston 35 in Fig. 2 travels to the right and the pressure chamber 2'? is filled with pressure fluid, causing the piston l to travel from its lower position shown in Fig. 2 to its upper position represented in Fig. 1. Since the pressure chamber 2% is under pressure transmitted from the ring-shaped space In through port 29, and since the ring-shaped area on the side towards piston 9 of the hollow auxiliar piston 5 is larger than the ring-shaped area of the operating piston 9 in the pressure chamber 26, the hollow piston 5 moves upward until bridge i2 reaches stop 38. Nuts I! and I3 are set in such a way that the opposed plunger will be lifted, a distance great enough to completely close the orifice of sprue I6 when motion is arrested by stop 30. This position indicates the largest quantity of molten metal which can be die-cast in the machine. The molten metal is always charged up to the upper edge of material and compression chamber I. If an amount below the maximumquantity is to be cast, nuts I1 and i8 are screwed in correspondingly, so that the smaller amount of molten metal also reaches the upper edge of the filling and compression chamber 5, the opposed piston being somewhat higher in this case.

After filling the material and compression chamber fiush with molten metal, the piston I9 travels downward together with the injection plunger 2, the push rods I3 beingalso moved downward by cross head I4. Directly before the injection plunger 2 enters the material and compression chamber i, that is just before it touches the molten metal in the chamber, the collars of the push rods I3 come into contact with bridge I2 causing the latter, including hollow piston 5, to travel downward when the plunger continues its motion. The downward motion is effected against the constant pressure exerted on the ring-shaped lower side of piston i9 and hollow piston 5. Due to the pressure in pressure chamber 25 piston 9, too, moves downward into the common cylinder 7, which on its part remains stationary because its larger piston area is under pressure from pressure chamber 21. Motion of piston Si and of the opposed piston 3 is stopped when the lower face of the operating piston 9 has reached stop 8 of cylinder 1. In this position the opposed plunger 3 has completely opened sprue I6. Injection plunger 2 and piston 5 move downward against the pressure prevailing in compression chamber 26, the sprue being now wide open. The plunger now produces in the molten metal a high pressure, causing the metal to pass through the sprue into the die 32, 33. As the upward force exerted on the large combined cylinderpiston I exceeds the downward force of the injection plunger by a large amount, it is insured that during this operation piston 1 remains stationary.

After the molten metal is forced into the-die, there remains a certain residual metal in the material and compression chamber I. By actuating the control mechanism 40, pressure in the die closing cylinder 34 and thus also in pressure chamber 2! of cylinder II is relieved. By properly dimensioning the forces necessary for the backward motion of die closing piston 35 and piston '1, it can be brought about that piston I is the first one to move downward. The injection plunger 2 can thus continue its downward motion, in the course of which it shears off the residual metal 3| from the part solidified in sprue IE, moving it completely out of the material and compression chamber. When injection plunger 2 remains stationary in the lower position represented in Fig. 2, piston I travels to its bottom position shown in Fig. 2. The faces of the two plungers are now a certain distance apart, which makes removal of the residual metal from the injection plunger or the opposed plunger but a simple operation. When piston I has moved to its bottom position, the die closing piston 35 starts its opening operation during which it travels to the extreme left position represented in Fig. 2, and, in doing so, pulls out of the sprue I6 the residual metal. Removal from the die can be carried out in any conventional manner.

By actuating control mechanism 4|, injection plunger 2 is returned by piston I9 into its starting position. The material and compression chamber I now completely open on the upper and lower ends represents a smooth cylinder easily accessible for cleaning and lubrication. This is an important advantage of the tube-like construction of the material and compression chamber.

For carrying out the next casting circle, die 32, 33 is closed in the manner described above. At the same time the filling and compression chamber I is closed from below by upward motion of opposed piston 3 effected by combined cylinderpiston l and ring-shaped piston 5, with piston 3 entering the material and compression chamber. Now the machine is ready for the next casting operation. r Y

11; maybe of advantageto install a th-rot't1ei36 in*line iil. By that*the piston -which,-- during its downward motion, would tendto quickly displace the" pressure fluid from the space 26, produces an-increased-pressure in space 26. This increased pressure produces a higher force on piston 9, insuringitherebythat. it follows promptly .andreliably. when bridge 12 is positively moved by 1 into contact withthe moltenmetal, and continues this motion under the action of the high pressure prevailing inchamb'er '26 with the same speed as injection plunger 2 untiL'upon piston 9 reaching ="stop 8,:sprue l6 is'completely opened'through the motion of opposed plunger '3. At this moment, with the opposed plunger 3 being stationary, injection plunger 2 can exert its full pressure, and force, under this full pressure, the molten metal into open sprue l6 and from there into the die. It is understood that the invention described above can be reduced to practice by other suitable applications, the essential factor being always that the injection plunger, during its forward stroke positively moves the transmitting means l2, 5, which, on their part are hydraulically connected to the opposed plunger in such a rigid manner that an immediate and quick opening of the sprue I6 is brought about practically without increased pressure in the molten metal, when the injection plunger 2, [9 comes into contact with the metal.

I claim:

1. A die-casting machine comprising an injection plunger and an opposed plunger, a tubelike compression chamber the upper end of which is the entrance opening for the injection plunger and the lower end being closed by the opposed plunger, a die, at least one sprue leading from the compression chamber to a laterally arranged die, a movable abutment mounted on the opposed plunger, the opposed plunger when in its innermost position'closing the sprue and being pressed against the movable abutment, a stationary stop to limit the movement of the movable abutment and of the opposed plunger in the sprue-closing position, driving means connected to the injection plunger positively engaging the movable abutment after an idle stroke portion which corresponds to the distance between the front face of the injection plunger in its uppermost position and the entrance opening of the compression chamber whereby during the next portion of the stroke the opposed plunger participates in the movement of the injection plunger and of the movable abutment so that while the sprue is opened by the opposed plunger, pressure is not yet exerted on the metal enclosed between the two moving plungers, a stop member limiting the movement of the opposed plunger which has just opened the sprue to cause the injection plunger in continuation of its stroke, to press the metal from the compression chamber through the sprue and into the die.

2. A die-casting machine comprising a sprue, a compression chamber, an injection plunger and second plunger which controls the entrance opening of the sprue leading to a mould cavity, a movable abutment mounted on the second plunger, the second plunger, when the injection plunger begins to move towards the compression chamber, closing the sprue and being pressed against the movable abutment by a pressure which is lower than an'oppo'sed -pressure; pressing the movableabutment against"a='stationary stop,=*dr-iving means connected to the injection 1 plunger and being exerted thereon between the two} plungers J 'until the' sprue has been fully opened and after the second'plungenhas been stopped bya'second stop, theinjection plunger continuing its" stroke and gpresses the metal from the "compression chamber into. the die. through the sprue.

.3, Edie-casting machine :comprising .an 1 in- 1 jection plunger andan opposed plunger. a tubelikefcompr'essi on chamber :the "upper "end of whi ch-is"'theientrance openingfor the injection "plunger 'andthe lower end'being closable *by' the opposed plunger, a movable abutment, at least one sprue leading from the compression chamber to a laterally arranged die, the opposed plunger which, in its innermost position, closes the sprue being under the influence of a pressure medium, said movable abutment being able to contact a stationary stop under a higer pressure to limit the movement of the movable abutment and of the opposed plunger in the sprueclosing position, driving means connected to the injection plunger and abutting the movable abutment shortly before the injection plunger enters the compression chamber thereby shifting the opposed plunger so that the metal enclosed between the two plungers is, without being pressed, moved correspondingly, and only after the opposed plunger has reached its fixed sprueopening position, the injection plunger pressing the metal from the compression chamber into the die by means of the sprue.

4. A die-casting machine comprising an injection plunger and an opposed plunger, a tubelike compression chamber the upper end of which is the entrance opening for the injection plunger and the lower end being closed by the opposed plunger, a die, at least one sprue leading from the compression chamber to a laterally arranged die, a movable abutment mounted on the opposed plunger, the opposed plunger when in its innermost position closing the sprue and being pressed against the movable abutment, a stationary stop to limit the movement of the movable abutment and of the opposed plunger in the sprue-closing position, driving means connected to the injection plunger positively engaging the movable abutment after an idle stroke portion which corresponds to the distance between the front face of the injection plunger in its uppermost position and the entrance opening of the compression chamber whereby during the next portion of the stroke the opposed plunger participates in the movement of the injection plunger and of the movable abutment so that while the sprue is opened by the opposed plunger pressure is not yet exerted on the metal enclosed between the two moving plungers, a stop member limiting the movement of the opposed plunger which has just opened the sprue to cause the injection plunger in continuation of its stroke, to press the metal from the compression chamber through the sprue and into the die, a hydraulically operated die-closing piston, a second hydraulically operated piston, a control mechanism by which both pistons are subjected to the same fluid pressure, the second piston forming the stop member and having a larger cross-section opposed to the fluid pressure than that of the die-closing piston, the fluid pressure which is exerted on the second piston to secure the fixed position of the stop member, being higher than the power exerted on the injection plunger to perform the working stroke, and the second piston followed by the injection plunger being first moved before the die-closing piston performs its die-opening stroke.

5. A die-casting machine according to claim 4, in which the movable abutmentis connected to ahollow piston in which a rod leading from the opposed plunger to a further piston is guided, a common cylinder provided for both the hollow piston and the further piston, the pressure of a fluid contained in the common cylinder being exerted on a small annular shoulder of the said further piston and pressing the opposed plunger against the movable abutment, the pressure exerted on the hollowpiston pressing the movable abutment against a'stationary stop which islarger than that exerted on the small annular shoulder of the said further piston.

WILIBALD A. 'VENUS.

REFERENCES CITED lhe following references are of record in the file of this patent:

UNITED STATES PATENTS Germany Dec. 2, 1931 

